1. Field
The present invention relates to a washing machine having balancers, and more particularly, to a washing machine, which reduces the vibration of a tub generated by the partial disposition of laundry in a dehydrating operation, and a method of controlling the same.
2. Description of the Related Art
Generally, washing machines, usually drum washing machines, are apparatuses that wash laundry by power generated when laundry is lifted and then dropped. A conventional drum washing machine includes a tub installed in a housing, which forms the external appearance of the washing machine, to contain water, a drum rotatably installed in the tub containing laundry, and a motor generating a driving force for rotating the drum.
In such a drum washing machine, when the drum is rotated at a high speed in a dehydrating operation under a condition that the laundry is not uniformly distributed in the drum, but is clustered on a specific part of the drum, the drum is eccentrically rotated on a rotary shaft and collides with the tub, thus generating vibration and noise. When repeated, parts of the washing machine including the drum and the tub are out of order or life spans of the parts are shortened.
In order to solve the above problems, Korean Patent Laid-Open Publication No. 1999-0038279 discloses a washing machine having balancers, which are provided on front and rear ends of a drum so as to reduce the vibration of a tub caused by the eccentric rotation of the drum.
Each of the balancers of the washing machine disclosed by the above Publication comprises a race installed on the front or rear end of the drum maintaining the dynamic balance of the drum when the drum is rotated at a high speed, balls made of steel and installed in the races such that they can move freely, and a viscous oil filling the inside of the race for adjusting the momentum of the balls. The race is formed by bonding ring-shaped upper and lower plates.
Therefore, when the drum is rotated under a condition that the drum cannot maintain its dynamic balance due to the unbalanced eccentric structure of the drum and the partial disposition of laundry in the drum, the balls made of steel compensate for the imbalance of the drum, thus allowing the drum to maintain the dynamic balance.
Each of the balancers of the conventional washing machine has a multi-race including at least two race parts, an inner race part and an outer race part, preventing the excessive vibration of the tub generated when the balls reach a balancing position, and the viscous oils having different viscosities and the balls having different sizes respectively filling the race parts, thus having high production costs. Further, the constitution of the races preventing the excessive vibration of the tub is not determined by precise calculation, but only reduces the probability of the vibration of the tub. Thus, the possibility of generating excessive vibration of the tub still remains. Accordingly, in order to further reduce the probability of the excessive vibration of the tub, a larger number of race parts are required.